This invention relates generally to light units, and more specifically, to methods and systems for use in testing a functional status of a light unit.
Colored signals are commonly used in railway systems to indicate route availability and/or speed requirements. At least some known signals include incandescent lights having colored covers. Other known signals include colored non-incandescent lights, such as light emitting diodes (LEDs). Typically, light emitting diodes are preferred because they have a longer life-span, operate with lower power consumption, and provide better visibility. Regardless of whether a railway system includes incandescent lights or LEDs, the signals are required to be tested periodically to determine their functional status.
Generally, incandescent lights are tested using known cold filament testing methods. Specifically, when the light is not in use, a plurality of repeated pulses are transmitted to the incandescent light over a predetermined time period. During the transmission of the pulses, the amount of current draw from the incandescent light is measured to ensure functionality of the light. Generally, cold filament testing is an acceptable testing methodology with incandescent lights because the lights require a warm-up time before visible light is transmitted therefrom. Because cold filament testing uses repeated pulses, the incandescent lights are not provided time to warm-up and, as such, no visible light is inadvertently emitted from the incandescent light during the testing process.
In contrast, non-incandescent lights have a quick warm-up time, and therefore, emit visible light during cold filament testing. Such light emission is unacceptable because railway operators may confuse the light emitted during testing as a warning signal. Accordingly, cold filament testing is generally unavailable when the railway system includes non-incandescent lights. One known solution to the unavailability of cold filament testing is to electrically couple the non-incandescent light to a standard VLD card and provide an intermediate set of electronics that make the non-incandescent light appear as an incandescent light to the VLD diagnostic routines. However, this approach fails to limit power requirements during testing, and increases the complexity and costs associated with testing the light unit.